It is known to have cellular telecommunications terminals that operate in a half-duplex mode i.e. they do not transmit and receive at the same time. An example of such a terminal is a GSM mobile telephone and some GPRS mobile telephones.
It is known to have cellular telecommunications terminals that operate in a full-duplex mode i.e. they transmit and receive at the same time. An example of such a terminal is a high-end GPRS mobile telephone and a WCDMA mobile telephone.
A dual mode telephone may therefore change its duplex capability by switching from a GSM mode of operation to a WCDMA mode of operation. The RF circuitry and antennas used for respectively operating in the GSM mode and WCDMA mode will typically be different and separate.
A key component of a full-duplex terminal is a duplexer which connects the transmitter and receiver to the antenna and prevents the symbols transmitted by the transmitter interfering with the symbols received by the receiver. Duplexers are expensive, consume power and have a large volume. It would therefore be desirable to reduce the use of duplexers or to use cheaper, less power hungry and smaller duplexers.
Currently duplexers are designed to provide enough isolation between the receiver and transmitter when the transmitter is operating at maximum power. If this constraint were relaxed, it may be possible to use cheaper, less power hungry and smaller duplexers.
There is a current trend towards the use of multiple antennas within a terminal. These antennas each have their own associated channels or may diversify a channel. However, the addition of multiple antennas typically also requires the use of multiple duplexers to isolate every receiver branch from every transmitter branch. It would be desirable to provide for the use of multiple antennas without the use of a duplexer at each antenna.